Hydrocarbon treating process



Jan. 24, 1950 H. H. \IOGE ET AL HYDROCARBON TREATING PROCESS Filed Aug.24, 1946 4 Sheets-Sheet l o m xm lso Paraffin N Buiglene Hea'rer lrwen'lors Her-veg H. Voge George M. Good Bernard 3. 6r el r I By iheirA++orneg= g?:

J" 24, 1950 H. H. VOGE ETAL HYDROCARBON TREATING .PROCESS 4 Sheets-Sheet3 Filed Aug. 24, 1946 .aopeay .aopnag .xowuo 1 .09.15

.aopeaa lnveniors Herve-g H. \loge .aqwaedag George M. Good 5 ihe'n"A1+orneg Patented Jan. 24, 1950 HYDROCARBON TREATING PROCESS l-lervey H.Voge, Berkeley, George M. Good, Al-

bany, and Bernard S. Greensfelder, Oakland, Calif., asslgnors to ShellDevelopment Company, San Francisco, Calif., a corporation of DelawareApplication August 24. 1946, Serial No. 692,882

8 (Ha. i

This invention relatesto the separation and/ or production of usefulproducts from lower boiling olefins, especially olefins having from 4 to6 carbon atoms and hydrocarbon mixtures containing sub stantialquantities of such olefins. In one embodiment of the invention, normalolefins are separated from hydrocarbon mixtures containing them as wellas their branched chain isomers through selective conversion of thebranched chain isomers into saturated hydrocarbons which may beseparated from the normal olefins by conventional separation processes.In other embodiments of the invention this selective conversion ofbranched chain olefins to saturated hydrocarbons is utilized to producean iso-paraffin and/or gasoline.

An object of the invention is to provide a new and improved method forthe separation of normal olefins from a hydrocarbon mixture containingthe same in admixture with an isomeric branched chain olefin. Thus, anobject is to provide a method for the separation of normal butylenesfrom refinery butylene fractions.

Another object of the invention is to provide a method for theproduction of iso-parafiins. Thus, an object of the invention is toprovide a method for the production of isobutane from butylene orrefinery butylene fractions and the production of isopentane fromamylene fractions.

A further object of the invention is to provide a method for theproduction of improved yields of alkylate gasoline having improvedvolatility from refinery butylene fractions.

These and other objects which will be apparent in the description of theinvention and its uses are attained through the catalytic treatment ofsuitable olefinic fractions under conditions to more or less selectivelyconvert the olefins having a branched chain into the correspondingisoparamns. Thus, the process of the invention in its more generalaspect involves reacting an olefinic hydrocarbon fraction containingsubstantial amounts of a normal olefin and an isomeric branched chainolefin in the vapor phase in the presence of a cracking catalyst at atemperature below that affording cracking of the hydrocarbon mixture butabove that at which substantial polymerization to higher boiling olefinstakes place and for a time adjusted to selectively convert branchedchain olefins to saturated products consisting largely of thecorresponding branched chain paramn.

The process is generally applicable to the treatment of lower boilinghydrocarbon fractions such operations. Preferred fractions are thosehaving from 4 to about 6 carbon atoms, i. e. boiling below about 70 C.Particularly suitable materials are the so-called refinery butylene andamylene fractions. In general, separation of one or more of thecomponents of such fractions is possible by the application ofconventional methods. However, a complete separation is too difiicult tobe feasible except on a small scale for special purposes. The usualrefinery butylene fraction represents the simplest case because of thefewer possible isomers. In this simplest case, certain separations canbe made quite readily. However, the separation of butene-l fromisobutylene is difficult. These two isomeric olefins boil within 1 ofone another and are generally quite similar in properties. However, apractical means for this separation is desirable, since these twoolefins are desired separately for different purposes. The normal olefinis desired, for example, as a starting material for the production ofbutadiene, whereas the isobutylene is desired separately as a startingmaterial in various syntheses.

The catalyst used in the process of the present invention is a crackingcatalyst. The term cracking catalyst is meant to designate that group ofcatalysts which is active in catalyzing the scission of 0-0 bonds, butwhich has no appreciable ability to catalyze the addition of hydrogen toan olefinic bond. Examples of such catalysts are the complexsilica-alumina, silica-magnesia, silicaas are commonly encountered invarious refinery lid zirconia-alumina, and alumina-boria crackingcatalysts and the activated clay cracking catalysts. Any of the vriousknown cracking catalysts of this general type (frequently referred to asclay-type cracking catalysts) may be used. The usual cracking catalystsrarely contain a hydrogenating component. However, occasionally ahydrogenating component (e. g. Mo, W, Co) is incorporated in a smallamount to aid in the catalyst regeneration or for other reasons. Suchcatalysts may be used in the process of the present invention, in theusual case where there is no appreciable free hydrogen present in thereaction zone. Ordinary hydrogenation with free hydrogen is avoided.Such hydrogenation, it is found, gives a totally different result.

The conditions of treating in the process of the present invention areimportant and critical. At high temperatures the cracking catalystcauses cracking of the olefinic feed. At low temperatures the crackingcatalyst causes polymerization of the olefins to high boiling polymers.The applicable temperatures constitute that range which lies betweenthese two extremes. The limits of acaaeae temperature, althoughcritical, cannot be stated to lie within definite limits for the generalcase since the limits depend upon the space velocity, upon theparticular olefin fraction treated, upon the particular catalyst used,and to some extent upon the purpose of the treatment. The governingfactors are analogous to those in catalytic cracking, which factors arewell known and understood. The conditions are adjusted in the knownmanner and according to known principles such that the temperature isbelow that afiording cracking of the hydrocarbon mixture, but above thatat which substantial polymerization to higher boiling olefins takesplace. The contact time is adjusted to decrease the bromine number to avalue corresponding approximately to the content of normal olefin in theproduct. While the critical limits of the applicable ranges ofconditions cannot be defined in absolute values for the general case,the following conditions are generally within the critical range and maybe considered as approximations of the applicable range:

Cd Fraction C5 Fraction Minimum temperature, O.. 325 308 Maximum ternerature, O 460 425 Minimum LH V 0.3 0.3 Maximum LHSV- 3.0 3.0

(Liquid hourly space velocity--LHSV-is defined terial fed to thereaction zone in this case is still lit) hill

higher depending upon the amount of hydrogen donor material included.The operation is preferably carried out at pressures from atmosphericpressure up to about atmospheres. The indicated liquid hourly spacevelocities are for substantially atmospheric pressure operation. As thepressure is increased, the liquid hourly space velocity should beadjusted in the known manner to afiord an approximately equivalentcontact time.

The contact time (LHSV) is adjusted such that the branched chain olefinor olefins in the feed are substantially completely converted. Inpractice some isomerization of the olefins usually takes place and as aconsequence it is not possible to produce a product completely free ofbranched chain olefins. However, when the branched chain olefins in thefeed have been substantially completely converted only a minor amount ofbranched chain olefins will be found in the product. The adjustment andcontrol of the contact time (LHSV) may 'be made through correlation withthe bromine number. The bromine number, which is easily determined bythe lmown methods, is a function of the total olefin content of thesample. Thus, the liquid hourly space velocity may be adjusted such thatthe bromine number of the product corresponds approximately to thecontent of normal olefin therein. When this condition pertains, thebranched chain olefins (except for the minor residue produced byisomerization as explained above) will have 'been substantiallycompletely reacted; a decrease in the liquid hourly space velocity willcause reaction of the normal olefins; an increase in the liquid hourlyspace velocity will give an incompletely converted product containingconsiderable amounts of branched chain olefins, from which product thedesired normal olefins cannot be easily separated. When the conditionsare properly adjusted the product contains only the above-mentionedminor amount of residual branched chain olefins and the desired normalolefins may be readily separated from the reaction mixture byconventional methods.

The separation of the residual normal olefins from the isoparaflinproduced may be effected by any one of a number of methods. In somecases a sharp fractionation may suffice. The preferred method is,however, through extraction of the normal olefins. Any one of the largenumber of known solvents may be used for this purpose. Examples of a fewsuitable solvents are sulfur dioxide, furfural, acetone-water, andsuliolane. Also, combination processes such as extractive distillationmay be applied.

In some cases it will not be desired to recover the normal olefins perse. Thus, the normal olefins in the reaction product may be reacted orconverted into a desired product instead of beingseparated. This allowsthe process of the invention to be advantageously applied for theproduction of gasoline. For example, the normal olefins may bepolymerized or alkylated in situ. Such applications of the process ofthe invention are described in more detail later in connection with thedrawings.

In the present process the branched chain olefin is selectively reactedand the primary reaction product is the corresponding branched chainparaffin. Thus, the process of the invention may, if desired, beconsidered from the standpoint of this reaction product, i.e. it may beutilized as a means of producing branched chain parafiins. For example,in combination with a dehydrogenation step, it may be utilized toproduce (separate) normal butylenes and isobutane from refinerybutane-butylene fractions, or, in combination with an olefinisomerization step, the entire normal butylenes may be utilized in theproduction of isobutane. Details of such applications are explainedbelow in connection with the drawings.

The formation of isoparafiin from the corresponding branched chainolefin in the present process takes place through a self-saturationreaction. In the simple case the necessary hydrogen comes from theconversion of part of the reactant to a carbonaceous residue. This carbonaceous residue is removed from the catalyst by burningin the knownmanner. As a consequence of this reaction, the yields of product arealways less than The yield may be improved, however, by the applicationof a material which under the conditions will donate hydrogen morereadily than the olefinic fraction treated. Cyclohexane, cyclohexene andrelated hydrocarbons, although known to be good sources of hydrogen, areof no particular value for this purpose. It is found, however, thattheir polycyclic counterparts such as decahydronaphthalene,tetrahydronaphthalene and related polycyclic hydroaromatic compounds maybe advantageously used. Thus, if such material or a fraction containingsubstantial amounts of such material is available, it may be mixed withthe olefinic feed to the reaction zone. In view of the high boilingpoint of such materials, they may be easily separated from the reactionproduct and cause no diificulty in the separation of the desired normalolefin. If a large supply of such d material is not available, therecovered material may be hydrogenated in a separate step using aconventional hydrogenation catalyst and free hydrogen and then reused.

Various features of the process of the inven tion and its modes ofapplication will perhaps be better understood upon consideration of thefollowing description of more specific applications. In the description,reference is had to the attacher' drawings wherein process fiows areshown by means of conventional diagrams, and wherein:

Figure it illustrates an application of the process for the separationof a monoolefin from an olefinic hydrocarbon fraction containing thenormal olefin in admixture with an isomeric branched chain olefin;

Figure II illustrates an application of the proccan for the productionof allrylate gasoline from an olefinic fraction;

Figure Hit illustrates a modified process for the production of normalpentenes and isopentape from refinery pentane-amylene fractions; and

Figure 1V illustrates a modified process for the production of anisoparafidn from a corresponding olefin.

These figures are schematic and do not show all details, as, forinstance, provision for removal of the light gases always formed insmall amounts in such processes.

Referring to the drawing, Figure l, the oleflnic feed. for instance arefinery butane-butylen iii-action having the following analysis:

Mole

per cent lsobutylene 23 Normal butylenes dill lsobutane 20 lil'orrnalbutane 1d entering via line i, is forced by pump 2 through coll. it ofheater ll wherein it is heated to the desired reaction temperature, forinstance 400 C. The pre-heated charge then passes via line to one or twoof the reactors t, l and El. ftlthough only one or two reactors may beused. it is preferable to employ at least three reactors since thisallows two reactors to be used continuously while the third isundergoing regeneration. Air or other oxidizing gas for regenerationenters via manifold line it. The spent regeneration gas is removedthrough manifold line it. Reactors t, l and it are filled with asuitable cracking catalyst such, for example, as pellets oi thesynthetic silica-alumina composite cracking catalyst or the treated claycracking catalyst now in common use. An excellent catalyst can be simplyand cheaply prepared by impregnating activated bauxite with silica orboric oxide. The reaction is carried out at a temperature between about325 C. and 45b" G. and at a pressure of about 30 p. s. i. g. The liquidhourly space velocity is adjusted at about it such that the olefincontent of the product in manifold line 9 is about d095, as determinedby the bromine number.

The product withdrawn from the reactor via line i? is passed toextractor it. Cooled solvent, for example, sulfolane, is introduced intothe top of extractor it via line it] and passes countercurrent to thefeed. A substantially saturated product consisting predominantly ofisobutane is withdrawn from the top of extractor it via line it. The fatsolvent is withdrawn from the bottom of extractor it and passed via pumpill into stripper it. Heat for stripping may be supplied to the stripperor to the feed as by heater ii. The stripped solvent is withdrawn fromthe bottom of stripper it and recirculated after cooling to theextractor. The stripped fraction consisting essentially of normalbutylenes is recovered from the overhead product of stripper it via lineit).

In the embodiment illustrated in Figure 11, the process is utilized toproduce superior yields of allrylate gasoline having improvedvolatility. The usual refinery butane-butylene fraction, for instancehaving the analysis shown above, is suitable for alkylatlon only if alarge supply of isobutane is available. In most refineries, however,there is not enough isobutane to balance the olefine. In many cases theexcess olefin is therefore polymerized. In the process illustrated,excellent yields of alkylate may be produced from the refinerybutane-butylene fractions without resort to extraneous sources ofmaterial. Thus. the necessary balance between the olefin and isobutaneis established in the feed by the present process. Also, since in thepresent process the isobutane is produced by selective reaction of thelsobutylene, the alkylate is produced essentially from normal butylenes.This gives a su perior alkylate product. Also, the conditions in thepresent process may be easilyadjusted to give a minor amount ofintermediate boiling isoparaffins which enhance the volatility of thealkylate.

Referring to Figure II, the feed, for example, a refinerybutane-butylene fraction such as mentioned above, entering via line M,is commlngled with a hydrogenated fraction rich in hydrogenatedpolycyclic aromatic hydrocarbons in line it. The mixture is forced bypump it through preheater coil 26 in furnace 25. The feed preheated toabout 400 C. passes via line it to one or more of the catalytic reactors2i, tfi and it. Reactors 2?, 2t and 2d are filled with granules of asolid cracking catalyst, for example, on alumina which is activated andimpregmated with 15% by weight B203. The conditions are regulated asdescribed in connection with the operation in Figure I. The productwithdrawn via line 30 and containing normal butylenes, isobutylene, a.small amount of gasoline and heavy oil is passed to fractionator 3iwherein the heavy oil is separated as a bottom product which iswithdrawn via line (it. This heavy oil is charged to reactor at whereinit is hydrogenated with hydrogen introduced via line 3%. Freshpolycyclic aromatic or hydroaromatic hydrocarbons may also be introducedvia line it. Reactor 333 is filled with any one of the many knownapplicable hydrogenation catalysts. A suitable catalyst by way ofexample is a pelleted mixture of sulfides of tungsten and nickel. Withthis catalyst typical conditions by way of example are as follows:temperature-350 C.; pressure- 700 p. s. i. g.; LHSV-l; and an excess ofhydrogen. The product passes via line 35 to separator it whereindissolved hydrogen is separated and withdrawn via line ill. Thehydrogenated prodnot is then commingled with the feed and passed to theheater via line 22 and pump 23 as described.

The overhead product from fractionator 3i is passed via line 38 to afractionator 39 wherein the C4 fraction is separated overhead from alight gasoline fraction which is withdrawn from the bottom via line ill.The overhead C4 fraction is passed via. line M to fractionator t8.Normal butane is removed as a product of the process aseaete via lineAlli. Isobutane is removed via line- Bil, cooler lil, surge tank 52, andis passed by pump I53 and line 54 to the alkylation unit. In thealkylation unit 42 normal butylenes and isobutane are caused to reactthrough the agency of a suitable alkylation catalyst. The alkylation.step may be carried out through any of the conventional processes.

passed via line 33 to fractionator M wherein it The alkylated product.is

approximate analysis:

Mole

per cent Isoa nylenes 37 Normal amylenes 28 Isopentane 17 Normal pentane13 enters via line 6|. This feed is commingled with a mixture ofhydrogenated heavy oil and amylenes introduced via line 62. The mixtureis passed through coils of heater E i wherein it is preheated to about350 C. The preheated mixture passes via line 65 to one or more ofreactors 65, 6'! and t8. Reactors 66, ill and I58 are filled withgranules of a cracking catalyst, for example, the treated clay catalystproduced by the Filtrol Corporation. The temperature may be, forexample, 400 C. The liquid hourly space velocity with respect to theolefinic feed may be about 3.9, and the liquid hourly space velocitywith respect to the total feed to the reaction zone may be about 8.Under these conditions the branched chain amylenes are not onlyconverted selectively to the corresponding saturated compounds, but

an appreciable amount of isomerization of the normal amylenes tobranched chain amylenes takes place. The product leaving the reactorsvia manifold line 69 passes to a fractionator Ill wherein a heavyfraction containing polycyclic aromatic hydrocarbons is separated. Thisheavy fraction is removed by line II and passes to reactor 72 wherein itis hydrogenated with hydrogen introduced via line I3. The product passesvia line M to a separator I5. Recovered hydrogen is removed by line I6and recycled or withdrawn as desired. The hydrogenated productcontaining substantial amounts of hydrogenated polycyclic aromatichydrocarbons is passed via lines TI and 62 to the feed line wherein itcommingles with the feed entering the preheater. If desired, freshhydrogenated polycyclic aromatics may be introduced with the feed vialine 6|.

The overhead fraction from fractionator III is passed to fractionatorI8. In fractionator 18 gasoline components produced in the process by aminor amount of cracking and destructive hydrogenation of the heavyrecycled stock are separated as a bottom fraction which is withdrawn vialine I9. The remainder consisting essentially of C hydrocarbon is passedvia line Ill) to extractor BI, wherein it is contacted with a solventwhich is selective for olefins, for example, dimethylsulfol-ane. Arafiinate passes overhead via line 82 to a fractionator w. The extractphase is passed via line at tea strippertfi,

d The fraction consisting of extracted olefins (mostly normal amylenes)is recovered overhead via line 86 as a product of the process. Thefraction fed to fractionator 83 consists largely of normal andisopentane. The isopentane is removed overhead via line 81 as a productof the process. The normal pentane is removed from fractionator 83 vialine 88 and passed through coil 89 of heater 90 wherein it is preheatedto a dehydrogenation temperature, for example, 550 C. The preheatedfraction in the vapor phase is passed via line QI to one or more ofreactors 92 and 93. These reactors are filled with granules of thedehydrogenation catalyst such, for example, as alumina which isactivated and impregnated with chromium oxide and/or molybdenum oxide.Manifold lines 96 and 95' are for the introduction and withdrawal ofregeneration gas. The product withdrawn from reactor 92 and/or 93 vialine 96 contains hydrogen, amylenes and pentanes. This product is passedthrough a separator 91, separated hydrogen. is passed to thehydrogenation reactor I2 via lines 98 and 12. The pentane,

amylene product is withdrawn via line E39 and. commingled with thehydrogenated cycled oil in line I52.

In an alternative process where it is desired to produce more normalamylene and less branched chain pentanes, all or a part of the materialin line 99 is passed via valved branch line I00 into the feed line tothe extractor Ill.

In the modification illustrated in Figure IV, the entire feed, exceptfor the unavoidable losses to coke, etc., is converted into the desiredisoparaflln.

Referring to Figure IV, the feed, for example, a refinerypentane-amylene fraction, is charged via line III] and pump III to coilH2 in a heater H3, wherein it is preheated to, for example, 400 C. Thepreheated feed in line II l is commingled with a fraction from line H5and the mixture is passed to one or more of reactors Ilii, I II and II8. These reactors are filled with crack-'- ing catalyst and areoperated as described in connection with the other figures to aifordreaction of the branched chain olefins without appreciable cracking orpolymerization. The reaction product. passes via line M9 to extractorI22. Extractor I20 and stripper I2I are operated as described inconnection with Figure I. The raffinate (paraffinic compounds of theproduct containing the isoparafdns produced in the reactors .I It, I IIand/or H8) is withdrawn as an overhead product of extractor I20 via lineI22. The olefinic components of the product (extract) consistingessentially of normal olefins are separated from the fat solvent instripper II and are removed overhead via line I23, cooler I24 and surgetank I25. This fraction is carried by line I26 and pump I2'I to heatingcoil I 28 in heater I29 wherein it is preheated to an isomerizationtemperature, for example, 475 C., and then passed via line I32 toreactor Ii-lI. Reactor I3I is filled with a catalyst efiective for theisomerization of normal olefins to the isoolefins. Any of the knowncatalysts suitable for this purpose may be used. One suitable catalystby Way of example is alumina which is activated and has been acidifiedby a thorough washing with aqueous hydrochloric acid. The reactionproduct consisting essentially of branched chain olefins and unconvertednormal olefins is commingled with the feed in line I I I as describedand serves to enrich the feed with isoolefins,

26 thereby increasing the efllciency in reactors Ht,

aceacae iii and lit. The cracking catalyst used in reactors lit, iii andlit generally has an appreciable isomerization ability. Therefore, theentire amount of olefin may be converted by repeated recycling of thenormal olefin to these reactors. However, the conditions in reactors Iit, i it and i it are not necessarily optimum for olefin isomerizationand consequently the application of the separate isomerization reactoriii allows a more eficient process.

The invention claimed is:

i. Process for the production of useful products from C4 fractionscontaining normal butylenes and isobutylene which comprises treating theC4 fraction in the presence of an added fraction rich in polycyclichydroaromatic hydrocarbons in the vapor phase with a cracking catalystof the group consisting of silica-alumina, silica-magnesia,silica-zirconia-alumina and alumina-boria cracking catalysts and theactivated clay cracking catalysts at a temperature between 325 C. andloll" C. and at a pressure between 1 and atmospheres, said conditionsbeing correlated in the known manner within said ranges to avoidsubstantial cracking of said olefins, discontinuing the treatment whenthe bromine number of the resulting product corresponds to the contentof normal butylenes in the mixture whereby the said isobutylene isselectively converted to isobutane, separating the product into a heavyoil containing polycyclic aromatic hydrocarbons, normally gaseousproducts and a gasoline fraction, hydrogenating said separated heavy oiland cycling it to the C4 iced as the added fraction rich in polycyclichydroaromatic hydrocarbons, subjecting the normally gaseous fraction toan alkylation treatment to product an alkylated product boiling withinthe gasoline range, and blending the product of alkylation with saidseparated gasoline fraction to produce a substantially saturated lowdensity stable gasoline having good anti-knock rating and a greatervolatility than that of the product oi alkylation alone.

2. Process for the production of useful roducts from hydrocarbonmixtures containing normal and branched chain olefins having from i toabout 6 carbon atoms which comprises treating the hydrocarbon mixtureenriched in branched chain clef-ins in the vapor phase with a crackingcatalyst of the group consisting of silica-alumina, silica-magnesia,silica-zirconia-alumina and alumina-boria cracking catalysts and theactivated clay cracking catalysts at a temperature between 3%" C. and450 C. and at a pressure between 1 and 10 atmospheres, said conditionsbeing correlated in the known manner within said ranges to avoidsubstantial cracking of said olefins, discontinuing said treatment whenthe bromine number of the resulting product corresponds to the contentof normal olefins in the mixture whereby the said branched chain olefinsare selectively converted to the corresponding isoparaiiins, separatingthe product by solvent extraction into a saturated fraction consistinglargely of branched chain paraihns and an unsaturated tractionconsisting largely of unchanged normal olefins, subjecting said fractionconsisting largely oi" normal olefins to a catalytic isomerizationtreatment to produce a mixture of normal and branched chain olefins richin branched chain oleilns, and utilizing said isomerized mixture toenrich the above said hydrocarbon mixture with branched chain olefins asabove specified.

3. Process for the production of useful products from hydrocarbonmixtures containing normal to i and branched chain olefins having from 4to about 6 carbon atoms which comprises treating such olefinic feed inthe presence of an added higher boiling fraction rich in polycyclichydroaromatic hydrocarbons and in the presence of added branched chainolefin produced as hereinafter set forth in the vapor phase with acracking catalyst of the group consisting of silica-alumina,silica-magnesia, silica-zirconia-alumina and alumina-boria crackingcatalysts and the activated clay cracking catalysts at a temperaturebetween 300 C. and 450 C. and at a pressure between l and 10atmospheres, said conditions being correlated in the known manner withinsaid ranges to avoid substantial cracking of said oleilns, discontinuingsaid treatment when the bromine number of the resulting productcorresponds to the content of said normal olefins in the mixture wherebythe said branched chain oleflns are selectively converted to thecorresponding branched chain parafilns, separating the product bysolvent extraction into a saturated fraction consisting largely ofbranched chain parafiins and an unsaturated fraction consisting largelyoi unchanged normal olefins, subjecting said fraction consisting largelyof normal oleflns to a catalytic isomerization treatment to produce amixture of normal and branched chain olefins rich in branched chainolefins, and treating said mixture in admixture with the olefinic feedas described above.

4. Process for the production of useful products from butane-butylenefractions which comprises treating a butane-butylene fraction in thepresence of an added butane-butylene fraction produced as hereinafterspecified in the vapor phase with a cracking catalyst of the groupconsisting of silica-alumina, silica-magnesia, silica-zirconiaaluminaand alumina-boria cracking catalysts and the activated clay crackingcatalysts at a temperature between 325 C. and 450 C. and at a pressurebetween i and 10 atmospheres, said conditions being correlated in theknown manner within said ranges to avoid substantial cracking of saidolefins, discontinuing said treatment when the bromine number of theresulting product corresponds to the content or normal butylenes in themixture whereby the isobutylene in the mixture is selectively convertedto isobutane, separating the product by solvent extraction into asaturated fraction consisting largely of isobutane and unconvertednormal butane and an unsaturated fraction consisting largely ofunchanged normal butylenes, separating said saturated fraction byfractional distillation into an isobutane fraction and a normal butanefraction, subjecting said normal butane fraction to a catalyticdehydrogenation, and commingling the product of said dehydrogenationwith said butane-butylene fraction specified above.

5. The process which comprises contacting a mixture of a straight chainolefin and an isomeric branched chain olefin having from 4 to 6 carbonatoms with a cracking catalyst of the group consisting ofsilica-alumina, silica-magnesia, silica-zirconia-alumina andalumina-boria cracking catalysts and the activated clay crackingcatalysts at a temperature between 300 C. and 450 C. and at a pressurebetween 1 and 10 atmospheres, said 0 conditions being correlated in theknown manner within said ranges to avoid substantial cracking of saidolefins, discontinuing said contact when the bromine number of theresulting product corresponds to the content of said straight chain ole-11a in the mixture whereby the said branched ll chain olefin isselectively converted to the corresponding isoparafin, and recoveringthe said straight chain olefin in concentrated form from the isoparafilnso produced.

6. The process which comprises contacting a mixture of a straight chainolefin and an isomeric branched chain olefin having from 4 to 6 carbonatoms in the presence of an added polycyclic hydroaromatic hydrocarbonwith a cracking catalyst of the group consisting of silica-alumina,silica-magnesia, silica-zirconia-alumina and alumina-boria crackingcatalysts and the activated clay cracking catalysts at a temperaturebetween 300 C. and 450 C. and at a pressure between 1 and 10atmospheres, said conditions being correlated in the known manner withinsaid ranges to avoid substantial cracking of said olefins, discontinuingsaid contact when the bromine number of the resulting productcorresponds to the content of said straight chain olefin in the mix turewhereby the said branched chain olefin is selectively converted to thecorresponding isoparamn, and recovering the said straight chain olefinin concentrated form from the isoparafiin so produced.

7. A process which comprises contacting a C4 fraction containingsubstantial amounts of normal butylenes and isobutylene with a crackingcatalyst of the group consisting of silica-alumina, silica-magnesia,silica-zirconia-alumina and alumina-boria cracking catalysts and theactivated clay cracking catalysts at a temperature between 325 C. and450 C. and at a pressure between 1 and 10 atmospheres, said conditionsbeing correlated in the known manner within said ranges to avoidsubstantial cracking of said olefins, discontinuing said contact whenthe bromine number of the resulting product corresponds to the contentof said normal butylenes in the mixture whereby said isobutylene isselectively converted l to isobutane, and recovering the said normalbutylenes in concentrated form from the isobutane so produced.

8. The process which comprises treating a Ca fraction containingsubstantial amounts of normal amylenes and branched chain amylenes witha cracking catalyst of the group consisting of sliica-alumina,silica-magnesia, silica-zirconia-alumina and alumina-boria crackingcatalysts and the activated clay cracking catalysts at a temperaturebetween 300 C. and 425 C. at a pressure between 1 and 10 atmospheres,said conditions being correlated in the known manner within said rangesto avoid substantial cracking of said olefins, discontinuing saidcontact when the bromine number of the resulting product corresponds tothe content of said straight chain amylenes in the mixture whereby saidbranched chain olefins are selectively converted to isopentane, andrecovering the said straight chain olefins in concentrated form from theisopentane so produced.

HERVEY H. VOGE. GEORGE M. GOOD. BERNARD S. GREEIISF'ELDER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS 846,480 France Sept. 18, 1939

5. THE PROCESS WHICH COMPRISES CONTACTING A MIXTURE OF A STRAIGHT CHAINOLEFIN AND AN ISOMERIC BRANCHED CHAIN OLEFIN HAVING FROM 4 TO 6 CARBONATOMS WITH A CRACKING CATALYST OF THE GROUP CONSISTING OFSILICA-ALUMINA, SILICA-MAGNESIA, SILICA-ZIRCONIA-ALUMINA ANDALUMINA-BORIA CRACKING CATALYSTS AND THE ACTIVATED CLAY CRACKINGCATALYSTS AT A TEMPERATURE BETWEEN 300*C. AND 450*C. AND AT A PRESSUREBETWEEN 1 AND 10 ATMOSPHERES, SAID CONDITIONS BEING CORRELATED IN THEKNOWN MANNER